Breeding and egg survival of a population of a salamander, Hynobius nebulosus tokyoensis Tago

Summary A population of a salamander, Hynobius nebulosus tokyoensis Tago was studied at Habu, Hinodemachi, in Tokyo during the breeding seasons from 1976 to 1978. Adults appeared in the pond were captured and marked individually by toe‐clipping. Egg sacks were counted and tagged with vinyl tapes for the marking. The annual egg production of this population was found to be constant, about 6500 eggs, and total number of breeding adults appeared in the pond also varied little during three years. The appearance of breeding adults in the pond and oviposition seemed to be influenced by the rise of temperature and rainfall. Males appeared earlier in the pond and stayed there for approximately 10 to 20 days. On the other hand, females appeared later in the pond and left there soon after laying eggs. Mean clutch size and body length of breeding adults appeared in the pond showed a tendency to decrease as time proceeded, which seemed to show that the smaller and younger the salamander was, the later it appeared in the pond. Owing to low temperature, the eggs laid earlier took more time to hatch than those laid later. The survival rate of eggs was 67.2% in 1976, 86.4% in 1977 and 81.2% in 1978. The loss rate of eggs laid in the early and late periods of oviposition was higher than that of eggs laid in the middle period.